Distribution centers and warehouses typically receive their products such as cases, boxes, open trays, stretch wrapped trays, etc. on a structured pallet, e.g. orderly positioned without gaps between them. Depalletizing systems are known in the art to remove the products from the pallet.
Technologies known as “bulk depalletizers” are used to remove a complete layer of products by pushing them from the pallet to an outfeed conveyor. In this situation, each layer of product is typically separated with a slip sheet.
Sometimes the products need to be depalletized and singulated so they can be stored in an automatic storage and retrieval system. There are usually two approaches to do this. The first is manual depalletizing, where operators pick the products individually and forward them on an outfeed conveyor. The other approach is to use a robot arm equipped with a layer depalletizing tool to remove the products layer by layer and drop them on an outfeed conveyor. Products are singulated after being depalletized in order to being stored in an automatic storage and retrieval system.
Robotized layer depalletizing tools are quite efficient when a large amount of products are found on each layer (small to medium sized products). Because of the complexity of the tool and the weight of the load, the cycle time is long and the efficiency (products per minute) drops when the products are large. In this later case, picking products one by one becomes a better approach. Also, with this approach, the products do not have to be singulated downstream as products are picked one by one from the pallet. This yields that the complete footprint is reduced compared to the approach that includes the layer depalletizer coupled with a singulator.
U.S. Pat. No. 8,248,620 B2, issued on Aug. 21, 2012 to Wicks and Maue and being titled “Object Detection Device” describes an object detecting device for detecting the existence and general placement of an object residing upon a surface. It uses a laser measuring scanner disposed on a linear actuator to allow the depalletizer to properly center a depalletizer tool in relation to the top layer to be picked from the load.
The device from Wicks and Maue uses a vision system to detect the top layer position only (e.g. outside corners of the top layer) and is unable to locate and position individual products on the layer.
U.S. Pat. No. 8,315,739 B2, issued on Nov. 20, 2012 to Dai and being titled “Determining the Position of an Object” describes a method for determining the position of at least one object present within a working range of a robot wherein an image is generated during a motion of the camera mounted on a robot.
The method from Dai is directed to known objects that are randomly stacked in a container, and does not allow to identify boxes that are adjacent to each other. Indeed, Dai's method looks for pieces with known dimensions that are distanced from each other and would not be operable when looking for products with no gaps therebetween. Also, in Dai, the camera is mounted on a robot. This slows down the process considering that the robot has to stop moving to take an image and wait for the result of the processing.
U.S. Pat. No. 6,332,750 B1, issued on Dec. 25, 2001 to Donner at al. and being titled “Method and Apparatus for Depalletizing Commodities” describes an apparatus for removing commodities from an upper side of a support, including means for monitoring the position of the support and at least one of the implement (e.g. slip sheet) and the selected commodity. A position sensor is located in the moving mean (e.g. tool).
The apparatus from Donner works by implying that slip sheets are present, which is not always the case. Also, similarly to the system by Dai, the position sensor is located on the tool, which implies immobilizing the tool frequently.
United States Patent Application No. 2014/0205403 A1, issued on Jul. 24, 2014 to Criswell and being titled “Automated Truck Unloader for Unloading/Unpacking Product from Trailers and Containers” describes an apparatus and method for unloading product from a trailer by executing a routine where a protruding product is identified and then unloaded by an industrial robot.
The approach taken by Criswell is based on the presence of a protruding product that can be identified by the vision system and therefore is inapplicable for depalletizing pallets where there are no protruding products when a complete layer is presented at the cell.
European Patent No. 0 911 603 B1, issued on Oct. 22, 1997 to Ersü and being titled “Method for the Determination of the Position of a Three-Dimensional Body” describes a method for the optical determination of the position of a finite rigid body where a selection of at least three lines of edges provided on the rigid body are identified.
The method from Ersü is applicable when the product to be positioned is already singulated from other products and as such cannot be used for products that need to be depalletized.
The PCT Patent Application Publication No. WO 2006117814 A1, published on Nov. 9, 2006 to Lodi Rizzini and being titled “Automatic Depalletizer” describes an apparatus and a method for depalletizing a pallet of blocks of material, where an optic sensor detects the distribution of the blocks located on the pallet before the blocks are picked and conveyed to the unloading station.
The depalletizer by Lodi Rizzini is aimed at depalletizing blocks of materials and is not suitable to depalletizing a wide variety of products such as boxes, cases, trays, etc. The optic sensor described by Rizzini is not versatile enough to detect and localize a wider variety of products, for example of any color and of variable rectangular shape.
A robotic system that allows depalletizing products as various as cases, boxes, trays and the like that are orderly positioned on a pallet with or without gaps between the products is thus desirable.